A pinch valve making use of a solenoid to pinch one or two flexible rubber tubes made by Brunswick-Technetics is known. A dialysis "single needle adapter" valve made by Vital Assists Inc., no longer in existence, is also known which operated in the same way as the Brunswick-Technetics valve. In this valve, a solenoid was used to activate a solenoid shaft moving transversely to the placement of the solenoid to pinch the rubber tubes in the valve. This valve however had the following drawbacks: a very large and heavy solenoid was required which in turn called for large power requirements, the valve was always on in one position, there was no feedback on the valve position through switches or other means, and there was no reasonable means of holding the valve in a partially opened position.
An electric hosecock to constrict the flow of fluid in a flexible tube is shown in U.S. Pat. No. 3,895,649 to Ellis, assigned to Delta Scientific Corporation of Lindenhurst N.Y. In this hosecock, a jaw is disposed adjacent the tubes whose flow is to be controlled, a plug is rotatably mounted in the hosecock body, and a coil spring is disposed around and secured to the plug. The spring has a straight end section and forms an arm which, when combined with one of the facing jaws, defines a channel for receiving a flexible tube. The spring arm is adapted to be engaged by an electromagnetic operator such as a solenoid. In a preferred embodiment, the spring arm extends between a pair of tubes which are disposed between a pair of facing jaws and can alternately constrict the fluid flow through one of the tubes.